Group III-V nitride semiconductors have been variously applied to optical devices such as blue and green light emitting diodes (LEDs), high speed switching devices such Metal Semiconductor Field Effect Transistor (MOSFET) and Hetero junction Field Effect Transistor (HEMT), and light sources of lighting devices or display devices. In particular, light emitting devices using group III nitride semiconductors have a direct transition-type bandgap corresponding to the range from visible rays to ultraviolet rays, and can realize high-efficiency light emission.
The nitride semiconductors are mainly used for LEDs or laser diodes (LDs), and studies have been continuously conducted to improve the fabrication process or light efficiency of the nitride semiconductors.